mozilla-central: changeset 288318:552aabbcd11631edd38087a55e8730db1384bdfc

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-001-ref.html
@@ -0,0 +1,161 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of height:auto grid, not top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.block {
+  border:5px solid;
+}
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-template-rows: 50px;
+  grid-column-gap: 12px;
+  border:5px solid;
+}
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+br { page-break-before:always; break-before:always; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 130px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+<span><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:3; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 18px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="block">
+</div></div></div>
+
+<div class="columns" style="height: 20px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="block" style="height:2px/*creates a Class C break opportunity at the end*/">
+</div></div></div>
+
+<div class="columns" style="height: 100px/*fragmentainer ends in the last row*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 70px/*fragmentainer ends in the grid gap between the rows */">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 40px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 13px/*fragmentainer ends in the grid start border */; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends above the grid*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-001.html
@@ -0,0 +1,122 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of height:auto grid, not top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-001-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 130px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 18px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+</div></div></div>
+
+<div class="columns" style="height: 20px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid" style="height:2px/*creates a Class C break opportunity at the end*/">
+</div></div></div>
+
+<div class="columns" style="height: 100px/*fragmentainer ends in the last row*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 70px/*fragmentainer ends in the grid gap between the rows */">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 40px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 13px/*fragmentainer ends in the grid start border */; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends above the grid*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-002-ref.html
@@ -0,0 +1,135 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation height:auto two row grid without grid items</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.block {
+  position:relative;
+  border:5px solid;
+}
+.grid {
+  display: grid;
+  position:relative;
+  grid-template-columns: 30px 30px 30px;
+  grid-template-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+}
+span { grid-row:1/2; position:absolute; top:0;bottom:0;right:0;left:0;background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+br { page-break-before:always; break-before:always; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 130px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span style="height:48px"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+</div></div></div>
+
+<div class="columns" style="height: 64px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span style="height:48px"><x></x></span>
+</div>
+<div class="grid b">
+</div></div></div>
+
+<div class="columns" style="height: 18px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="block">
+<span style="height:0"></span>
+</div></div></div>
+
+<div class="columns" style="height: 20px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="block t" style="height:2px">
+<span style="height:0px"></span>
+</div>
+<div class="block b" style="margin-top:6px;height:0px">
+</div></div></div>
+
+<div class="columns" style="height: 100px/*fragmentainer ends in the last row*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span style="height:48px"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+</div></div></div>
+
+<div class="columns" style="height: 70px/*fragmentainer ends in the grid gap between the rows */">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span style="height:48px"><x></x></span>
+</div>
+<div class="grid b">
+</div></div></div>
+
+<div class="columns" style="height: 40px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span><x></x></span>
+</div>
+<div class="grid b">
+</div></div></div>
+
+<div class="columns" style="height: 13px/*fragmentainer ends in the grid start border */; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span><x></x></span>
+</div>
+<div class="grid b">
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends above the grid*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span><x></x></span>
+</div>
+<div class="grid b">
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span><x></x></span>
+</div>
+<div class="grid b">
+</div></div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-002.html
@@ -0,0 +1,110 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation height:auto two row grid without grid items</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-002-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  position:relative;
+  grid-template-columns: 30px 30px 30px;
+  grid-template-rows: 50px 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { position:absolute; top:0;bottom:0;right:0;left:0;background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 130px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 64px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 18px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid" style="grid-template-rows:auto">
+<span></span>
+</div></div></div>
+
+<div class="columns" style="height: 20px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid" style="grid-template-rows:auto; height:2px/*creates a Class C break opportunity at the end*/">
+<span></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*fragmentainer ends in the last row*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 70px/*fragmentainer ends in the grid gap between the rows */">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 40px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 13px/*fragmentainer ends in the grid start border */; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends above the grid*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-003-ref.html
@@ -0,0 +1,138 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation height:auto grid with first grid row at top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.block {
+  border:5px solid;
+  border-top-width:0;
+  border-bottom-width:10px;
+}
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  border-top-width:0;
+  border-bottom-width:10px;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+br { page-break-before:always; break-before:always; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 120px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid t">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+<span><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:3; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="block">
+</div></div></div>
+
+<div class="columns" style="height: 10px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="block" style="height:2px/*creates a Class C break opportunity at the end*/">
+</div></div></div>
+
+<div class="columns" style="height: 90px/*fragmentainer ends in the last row*/">
+<div style="background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 60px/*fragmentainer ends in the grid gap between the rows */">
+<div style="background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 30px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-003.html
@@ -0,0 +1,105 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation height:auto grid with first grid row at top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-003-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  border-top-width:0;
+  border-bottom-width:10px;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 120px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid">
+</div></div></div>
+
+<div class="columns" style="height: 10px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid" style="height:2px/*creates a Class C break opportunity at the end*/">
+</div></div></div>
+
+<div class="columns" style="height: 90px/*fragmentainer ends in the last row*/">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 60px/*fragmentainer ends in the grid gap between the rows */">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 30px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-004-ref.html
@@ -0,0 +1,166 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation with first grid row at top-of-page and Class C break opportunities</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.block {
+  border:5px solid;
+  border-top-width:0;
+  border-bottom-width:10px;
+  height: 120px;
+}
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  border-top-width: 0;
+  border-bottom-width: 10px;
+  align-content: center;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+.grid.t {padding-top:4px;}
+
+.br1 { height:1px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 122px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid t" style="height:112px; padding-bottom:4px;">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div>
+<div style="height:2px;"></div>
+<div class="block" style="border-top-style:none; height:0px;">
+</div></div></div>
+
+<div class="columns" style="height: 122px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="block">
+</div></div></div>
+
+<div class="columns" style="height: 90px/*fragmentainer ends in the last row*/">
+<div style="background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="br1"></div>
+<div class="grid b" style="padding-bottom:16px">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 60px/*fragmentainer ends in the grid gap between the rows */">
+<div style="background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid m" style="padding-bottom:10px">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div>
+<div class="block" style="border-top-style:none; height:6px;">
+</div>
+</div></div>
+
+<!--  TODO XXX depends on bug 1238294
+
+<div class="columns" style="height: 30px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="background:grey">
+<div class="br1"></div>
+<div class="grid m">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid m">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div>
+<div class="block" style="margin-top:-19px; border-top-style:none; height:20px;">
+</div>
+</div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="background:grey">
+<div class="br1"></div>
+<div class="grid m">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid m">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div>
+<div style="background:black; padding-bottom:10px;"></div>
+</div></div>
+
+<div class="columns" style="height: 2px/*fragmentainer ends between the start border but before the first row */">
+<div style="background:grey;">
+<div class="br1"></div>
+<div class="grid m">
+<span><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+<span class="t"><x></x></span>
+</div>
+<div class="grid m">
+<span><x></x></span>
+<span class="b" style="height:11px; background:cyan"><x></x></span>
+<span class="b"style=""><x></x></span>
+</div>
+<div style="background:black; padding-bottom:10px;"></div>
+</div></div>
+
+-->
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-004.html
@@ -0,0 +1,115 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation with first grid row at top-of-page and Class C break opportunities</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-004-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  border-top-width: 0;
+  border-bottom-width: 10px;
+  height: 120px; /* 4px before/after first/last row are Class C break opportunities */
+  align-content: center;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 122px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 122px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid">
+</div></div></div>
+
+<div class="columns" style="height: 90px/*fragmentainer ends in the last row*/">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 60px/*fragmentainer ends in the grid gap between the rows */">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<!--  TODO XXX depends on bug 1238294
+
+<div class="columns" style="height: 30px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 2px/*fragmentainer ends between the start border but before the first row */">
+<div style="background:grey">
+<div class="grid">
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div></div>
+
+-->
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-005-ref.html
@@ -0,0 +1,149 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of height:auto grid, not top-of-page, forced breaks</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+.br1 { height:1px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*two rows would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b">
+<span class="b"><x></x></span>
+<span class="b" style="grid-area:1/3; height:6px; background:cyan"><x></x></span>
+<span style="grid-area:1/3; align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:30px">
+<div style="padding-top:10px; background:grey">
+<div class="grid break-before">
+</div></div></div>
+
+<div class="columns" style="height: 60px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:40px;"></div>
+<div class="grid">
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span style="align-self:end; grid-area:1/1; background:pink"><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="height:6px; background:cyan"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span style="align-self:end; grid-area:1/1; background:pink"><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="height:6px; background:cyan"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:90px;"></div>
+<div class="grid">
+<span style="height:35px"><x></x></span>
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="grid-area:2/1; align-self:end; background:pink"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 80px/*one row fits in 1st column, two in 2nd column, but forced break there*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div class="grid m">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span class="b" style="background:cyan"><x></x></span>
+<span style="grid-area:1/1; align-self:end; background:pink"><x></x></span>
+</div>
+<div style="height:50px"></div>
+<div class="grid b">
+<span style=""><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 160px/*everything would fit in 1st column*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid t">
+<span class="t" style="grid-row: span 2"><x></x></span>
+<span style="grid-row: span 2"><x></x></span>
+</div>
+<div style="height:53px"></div>
+<div class="grid b">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-005.html
@@ -0,0 +1,133 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of height:auto grid, not top-of-page, forced breaks</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-005-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+m { display:block; padding-top:10px; }
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*two rows would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:30px">
+<div style="padding-top:10px; background:grey">
+<div class="grid break-before">
+</div></div></div>
+
+<div class="columns" style="height: 60px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span class="break-before"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span class="break-after" style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span class="break-before" style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 80px/*one row fits in 1st column, two in 2nd column, but forced break there*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span style="grid-row:3"><x></x></span>
+<span class="break-after" style="grid-row:span 2; background:cyan"><x></x></span>
+<span class="break-before" style="grid-row:2; align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 160px/*everything would fit in 1st column*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span class="break-after" style="grid-row: span 3"><x></x></span>
+<span class="break-after" style="grid-row: span 2"><x></x></span>
+</div>
+</div></div>
+
+<!-- TODO XXX bug 775628? (break-after on last row should propagate to container)
+<div class="columns" style="height: 135px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span class="break-after" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+<div style="height:20px;background:yellow"></div>
+</div></div>
+-->
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-006-ref.html
@@ -0,0 +1,116 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of height:auto grid, not top-of-page, item break-inside:avoid</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.br1 { height:94px; border-width:5px; border-top-style:solid; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 110px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span><i></i><i></i><i></i><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 70px/*item will be INCOMPLETE*/">
+<div style="background:grey">
+<div class="grid">
+<span><i></i><i></i><i></i><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*item will be INCOMPLETE*/">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><i></i><i></i><i></i><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 140px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span style="grid-row:span 3"><x></x></span>
+<span style="grid-row:span 2"><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><x></x></span></div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-auto-rows: 50px; height:50px;">
+<span class="t" style="grid-row:span 2; height:49px; overflow:hidden"><i></i><i></i><i></i><x></x></span>
+</div>
+<div style="height:44px"></div>
+<div class="grid b" style="grid-auto-rows: 50px; height:50px;">
+<span class="b" style="grid-row:span 2; height:11px; overflow:hidden"><i style="margin-top:0;height:2px"></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="br1"></div>
+<div class="grid b" style="grid-auto-rows: 50px; height:116px;">
+<span style="grid-row:span 2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="br1"></div>
+<div class="grid b" style="grid-auto-rows: 50px; height:116px; grid-gap:0;">
+<span style="grid-row:span 2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="br1"></div>
+<div class="grid b" style="grid-auto-rows: 50px; height:116px; grid-gap:0;">
+<span style="height:100px; background:pink"><x></x></span>
+<span style="grid-row:span 2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-006.html
@@ -0,0 +1,108 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of height:auto grid, not top-of-page, item break-inside:avoid</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-006-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 110px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span class="avoid-break"><i></i><i></i><i></i><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 70px/*item will be INCOMPLETE*/">
+<div style="background:grey">
+<div class="grid">
+<span class="avoid-break"><i></i><i></i><i></i><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*item will be INCOMPLETE*/">
+<div style="background:grey">
+<div class="grid">
+<span class="avoid-break" style="grid-row:span 2"><i></i><i></i><i></i><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 140px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span style="grid-row:span 3"><x></x></span>
+<span class="avoid-break" style="grid-row:span 2"><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><x></x></span></div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-auto-rows: 50px;">
+<span class="avoid-break" style="grid-row:span 2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-auto-rows: 50px; height:116px;">
+<span class="avoid-break" style="grid-row:span 2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-auto-rows: 50px; height:116px; grid-gap:0;">
+<span class="avoid-break" style="grid-row:span 2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-auto-rows: 50px; height:116px; grid-gap:0;">
+<span style="height:100px; background:pink"><x></x></span>
+<span class="avoid-break" style="grid-row:span 2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-007-ref.html
@@ -0,0 +1,134 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of height:auto grid, not top-of-page, forced break growing 'fr' row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0;">
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 80px; grid-gap:0;">
+<span class="m"><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 30px; grid-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 92px; grid-row-gap:0;">
+<span class="m" style="height:10px; background:blue; margin: 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3"><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 30px; grid-row-gap:0;">
+<span class="b" style="grid-column:3"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:50px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+<div class="grid m" style="grid-template-rows: 92px; grid-row-gap:0;">
+<span class="m"><x></x></span>
+<span class="m" style="height:11px; color:blue; background:blue; margin: 0 1px; border-width:0"></span>
+</div>
+<div class="grid b" style="grid-template-rows: 30px; grid-row-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 50px; grid-gap:0;">
+</div>
+<div class="grid m" style="grid-template-rows: 1fr; grid-gap:0; height:100px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-007.html
@@ -0,0 +1,104 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of height:auto grid, not top-of-page, forced break growing 'fr' row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-007-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px 1fr 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px 1fr 50px;">
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow row 2*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px 1fr 50px; grid-gap:0;">
+<span style="grid-row:2/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-008-ref.html
@@ -0,0 +1,132 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of height:auto grid, top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  border-top-width:0;
+  align-content: start;
+}
+span { padding-top:20px; background:lime; border:1px solid black; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 94px">
+<div style="background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:82px">
+<span style="height:50px;"><i style="height:54px"></i></span>
+<span style="height:60px"><i></i><i></i><i></i></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0;">
+<span></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 94px">
+<div style="background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:82px">
+<span class="t"></span>
+<span style="height:50px;"><i style="height:54px"></i></span>
+<span style="height:60px"><i></i><i></i><i></i></span>
+</div>
+<div style="height:12px"></div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0;">
+<span class="b"></span>
+<span class="m" style="padding:0; height:6px; background:blue; margin: 0 1px; border-width:0"></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 94px">
+<div style="background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:82px">
+<span class="t"></span>
+<span style="height:50px"><i style="height:54px"></i></span>
+<span style="height:60px"><i></i><i></i><i></i></span>
+</div>
+<div class="grid m" style="grid-template-rows: 80px; grid-gap:0;">
+<span class="m"></span>
+<span class="m" style="padding:0; height:6px; background:blue; margin: 0 1px; border-width:0"></span>
+</div>
+<div class="grid b" style="grid-template-rows: 30px; grid-gap:0;">
+<span class="b"></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 94px">
+<div style="background:grey">
+<div class="grid t" style="grid-template-rows: 5px; grid-row-gap:0; height:5px">
+<span class="t" style="grid-column:3"></span>
+</div>
+<div style="height:88px"></div>
+<div class="grid m" style="grid-template-rows: 1fr; grid-row-gap:0; height:82px">
+<span style="height:50px"><i style="height:54px"></i></span>
+<span style="height:60px"><i></i><i></i><i></i></span>
+<span class="m"></span>
+</div>
+<div class="grid m" style="grid-template-rows: 92px; grid-row-gap:0;">
+<span class="m" style="padding:0; height:6px; background:blue; margin: 0 1px; border-width:0"></span>
+<span class="m" style="grid-column:3"></span>
+</div>
+<div class="grid b" style="grid-template-rows: 30px; grid-row-gap:0;">
+<span class="b" style="grid-column:3"></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 94px">
+<div style="background:grey">
+<div class="grid t" style="grid-template-rows: 5px; grid-row-gap:0; height:5px">
+<span class="t"></span>
+</div>
+<div style="height:88px"></div>
+<div class="grid m" style="grid-template-rows: 1fr; grid-row-gap:0; height:82px">
+<span class="m"></span>
+<span style="height:50px"><i style="height:54px"></i></span>
+<span style="height:60px"><i></i><i></i><i></i></span>
+</div>
+<div class="grid m" style="grid-template-rows: 92px; grid-row-gap:0;">
+<span class="m"></span>
+<span class="m" style="padding:0; height:6px; background:blue; margin: 0 1px; border-width:0"></span>
+</div>
+<div class="grid b" style="grid-template-rows: 30px; grid-row-gap:0;">
+<span class="b"></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-008.html
@@ -0,0 +1,95 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of height:auto grid, top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-008-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  border-top-width:0;
+  align-content: space-evenly;
+}
+span { padding-top:20px; background:lime; border:1px solid black; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 94px/*trigger OVERFLOW_INCOMPLETE for the item*/">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i></span>
+<span style="grid-row:2"></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 94px/*trigger OVERFLOW_INCOMPLETE for the item*/">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 2"></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 94px/*trigger OVERFLOW_INCOMPLETE for the item*/">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 4"></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 94px/*trigger INCOMPLETE for the item*/">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 5px 1fr 50px;">
+<span style="grid-row:2; height:50px"><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 94px/*trigger INCOMPLETE for the item*/">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 5px 1fr 50px;">
+<span style="grid-row:1/span 5"></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-009-ref.html
@@ -0,0 +1,161 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of definite height, not top-of-page, forced breaks</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*two rows would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b" style="height:60px">
+<span class="b"><x></x></span>
+<span class="b" style="grid-area:1/3; height:6px; background:cyan"><x></x></span>
+<span style="grid-area:1/3; align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:30px">
+<div style="padding-top:10px; background:grey">
+<div style="height:90px;border:5px solid;"></div>
+</div></div>
+
+<div class="columns" style="height: 60px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:50px;"></div>
+<div class="grid t">
+<span><x></x></span>
+</div>
+<div style="height:60px; border:5px solid; border-top-width:0;">
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b" style="padding-bottom:30px">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span style="align-self:end; grid-area:1/1; background:pink"><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="height:6px; background:cyan"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b" style="padding-bottom:30px">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span style="align-self:end; grid-area:1/1; background:pink"><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="height:6px; background:cyan"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:90px;"></div>
+<div class="grid" style="padding-bottom:18px">
+<span style="height:35px"><x></x></span>
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="grid-area:2/1; align-self:end; background:pink"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 97px/*everything would fit in 1st column, except bottom border*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:87px;"></div>
+<div class="grid t" style="padding-bottom:18px">
+<span style="height:35px"><x></x></span>
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="grid-area:2/1; align-self:end; background:pink"><x></x></span>
+</div>
+<div class="grid b"></div>
+</div></div>
+
+<div class="columns" style="height: 80px/*one row fits in 1st column, two in 2nd column, but forced break there*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div class="grid m">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span class="b" style="background:cyan"><x></x></span>
+<span style="grid-area:1/1; align-self:end; background:pink"><x></x></span>
+</div>
+<div style="height:50px"></div>
+<div class="grid b">
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 160px/*everything would fit in 1st column*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid t">
+<span class="t" style="grid-row: span 2"><x></x></span>
+<span style="grid-row: span 2"><x></x></span>
+</div>
+<div style="height:53px"></div>
+<div style="height:18px; border:5px solid; border-top-width:0;">
+<span class="b" style="display:block;height:29px;width:28px"></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-009.html
@@ -0,0 +1,144 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of definite height grid, not top-of-page, forced breaks</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-009-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  height: 90px;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+m { display:block; padding-top:10px; }
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*two rows would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:30px">
+<div style="background:grey"><m></m>
+<div class="grid break-before">
+</div></div></div>
+
+<div class="columns" style="height: 60px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span class="break-before"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span class="break-after" style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span class="break-before" style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 97px/*everything would fit in 1st column, except bottom border*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span class="break-before" style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 80px/*one row fits in 1st column, two in 2nd column, but forced break there*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span style="grid-row:3"><x></x></span>
+<span class="break-after" style="grid-row:span 2; background:cyan"><x></x></span>
+<span class="break-before" style="grid-row:2; align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 160px/*everything would fit in 1st column*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span class="break-after" style="grid-row: span 3"><x></x></span>
+<span class="break-after" style="grid-row: span 2"><x></x></span>
+</div>
+</div></div>
+
+<!-- TODO XXX bug 775628? (break-after on last row should propagate to container)
+<div class="columns" style="height: 135px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span class="break-after" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+<div style="height:20px;background:yellow"></div>
+</div></div>
+-->
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-010-ref.html
@@ -0,0 +1,48 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation in print context of height:auto grid, not top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 1in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+br { page-break-after:always; break-after:always; display:block; height:1px; }
+
+</style>
+</head>
+<body>
+
+<div style="padding-top:0.5in; background:grey">
+<div class="grid t">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+<span><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:0.54in; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:3; align-self:end; background:pink"><x></x></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-010.html
@@ -0,0 +1,43 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation in print context of height:auto grid, not top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-010-ref.html">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 1in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+  align-content: start;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+
+</style>
+</head>
+<body>
+
+<div style="padding-top:0.5in; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:1.5in; background:cyan"><x></x></span>
+<span><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-011-ref.html
@@ -0,0 +1,49 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation in print context of height:auto grid with first grid row at top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 1in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+  border-top-width: 0;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+br { page-break-after:always; break-after:always; display:block; height:1px; }
+
+</style>
+</head>
+<body>
+
+<div style="background:grey">
+<div class="grid t">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+<span><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:0.54in; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:3; align-self:end; background:pink"><x></x></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-011.html
@@ -0,0 +1,44 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation in print context of height:auto grid with first grid row at top-of-page</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-011-ref.html">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 1in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+  border-top-width: 0;
+  align-content: start;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+
+</style>
+</head>
+<body>
+
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:1.5in; background:cyan"><x></x></span>
+<span><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-012-ref.html
@@ -0,0 +1,49 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation in print context of height:auto grid, not top-of-page, forced breaks</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 0.5in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+  border-top-width: 0;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+br { page-break-after:always; break-after:always; display:block; height:1px; }
+
+</style>
+</head>
+<body>
+
+<div style="padding-top:0.5in; background:grey">
+<div class="grid t">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid b">
+<span><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:0.15in; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:3; align-self:end; background:pink"><x></x></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-012.html
@@ -0,0 +1,46 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation in print context of height:auto grid, not top-of-page, forced breaks</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-012-ref.html">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 0.5in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+  border-top-width: 0;
+  align-content: start;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+
+</style>
+</head>
+<body>
+
+<div style="padding-top:0.5in; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:0.6in; background:cyan"><x></x></span>
+<span><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-013-ref.html
@@ -0,0 +1,52 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation in print context of height:auto grid, item break-inside:avoid</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 1in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+br { page-break-after:always; break-after:always; display:block; height:1px; }
+
+</style>
+</head>
+<body>
+
+<div style="padding-top:1in; background:grey">
+  <div class="grid t">
+    <span class="t"><x style="height:auto"></x></span>
+  </div>
+  <div class="grid b" style="border-color:transparent; grid-auto-rows: 0;">
+    <span class="b"><x style="height:0.04in"></x></span>
+  </div>
+</div>
+
+<div style="padding-top:0.91in; background:grey;">
+  <div class="grid t" style="height:0.9in">
+    <span class="t" style="height:0.86in"><x></x></span>
+  </div>
+</div>
+  <div class="grid b" style="border-color:transparent; grid-auto-rows: 0;">
+    <span class="b"><x style="height:0.04in"></x></span>
+  </div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-013.html
@@ -0,0 +1,44 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation in print context of height:auto grid, item break-inside:avoid</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-013-ref.html">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 1in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+</style>
+</head>
+<body>
+
+<div style="padding-top:1in; background:grey">
+<div class="grid">
+<span class="avoid-break"><x></x><x></x><x></x><x></x><x></x></span>
+</div></div>
+
+<div style="padding-top:1in; background:grey">
+<div class="grid" style="align-content:end; grid-auto-rows:auto; height:1in">
+<span xclass="avoid-break"><x></x><x></x><x></x><x></x><x></x></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-014-ref.html
@@ -0,0 +1,39 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation in print context of height:auto grid, item break-inside:avoid</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 1in;
+  border: 0.1in solid;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+i { display:block; height:0.1in; background:blue; }
+
+</style>
+</head>
+<body>
+
+<div style="padding-top:1in; background:grey">
+<div class="grid" style="grid-template-rows: .91in 1in;">
+<span style="height:0.2in"><i style="height:1.5in"></i><x></x></span>
+<span style="height:0.25in"><i></i><i></i><i></i><x></x></span>
+<span style="grid-area:2/2"><x></x></span>
+</div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-014.html
@@ -0,0 +1,44 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html lang="en-US" class="reftest-print"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation in print context of height:auto grid, item break-inside:avoid</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-014-ref.html">
+  <style type="text/css">
+@page { size:5in 3in; margin:0.5in; }
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 0.6in 0.6in 0.6in;
+  grid-auto-rows: 1in;
+  grid-gap: 0.1in;
+  border: 0.1in solid;
+  align-content: start;
+}
+span { display:block; background:lime; border:0.05in solid black; }
+x { display:block; height:0.2in; }
+i { display:block; height:0.1in; background:blue; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+</style>
+</head>
+<body>
+
+<div style="padding-top:1in; background:grey">
+<div class="grid" style="grid-template-rows: 1fr 1in; grid-gap:0;">
+<span style="height:0.2in"><i style="height:1.5in"></i><x></x></span>
+<span class="avoid-break" style="height:0.25in"><i></i><i></i><i></i><x></x></span>
+<span style="grid-area:2/2"><x></x></span>
+</div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-015-ref.html
@@ -0,0 +1,128 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation edge cases</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  height: 90px;
+  grid-template-columns: 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+
+</style>
+</head>
+<body>
+
+<!-- grid wrapped in inline -->
+<div class="columns" style="height: 40px">
+<div style="padding-top:2px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<!-- grid wrapped in inline with orthogonal writing-mode -->
+<div class="columns" style="width: 40px; height:40px;">
+<div style="padding-top:2px; background:grey">
+<div class="grid" style="overflow:hidden; writing-mode:vertical-lr">
+<span style="grid-row:span 2;"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<!-- grid wrapped in overflow:hidden block -->
+<div class="columns" style="height: 40px; margin-top:70px">
+<div style="padding-top:2px; background:grey">
+<div class="grid" style="overflow:hidden">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<!-- grid wrapped in FIELDSET block -->
+<div class="columns" style="height: 40px; margin-top:70px">
+<div style="padding-top:2px; background:grey">
+<div style="display:block; overflow:hidden; border:none; padding:0; margin:0">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></div></div></div>
+
+<!-- grid wrapped in FIELDSET inline -->
+<div class="columns" style="height: 40px; margin-left:200px">
+<div style="padding-top:2px; background:grey">
+<div style="display:inline-block; overflow:hidden; border:none; padding:0; margin:0">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></div></div></div>
+
+<!-- grid wrapped in FIELDSET overflow:hidden block -->
+<div class="columns" style="height: 40px; margin-left:400px">
+<div style="padding-top:2px; background:grey">
+<div style="display:block; overflow:hidden; border:none; padding:0; margin:0; width:-moz-min-content">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></div></div></div>
+
+<!-- grid with orthogonal writing-mode to fragmentainer -->
+<div class="columns" style="height: 40px; margin-top:70px">
+<div style="padding-top:2px; background:grey">
+<y>
+<div class="grid" style="overflow:hidden; writing-mode:vertical-lr">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></y></div></div>
+
+<!-- vertical grid and fragmentainer with intermediary horizontal writing-mode inline -->
+<!-- XXX bug 1242660: remove the visibility:hidden DIV when we know what the rendering should be -->
+<div style="visibility:hidden">
+<div class="columns" style="width: 50px; writing-mode:vertical-lr; margin-top:70px">
+<div style="padding-top:2px; background:grey">
+<y style="writing-mode:horizontal-lr">
+<div class="grid" style="writing-mode:vertical-lr">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></y></div></div>
+</div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-015.html
@@ -0,0 +1,134 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation edge cases</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-015-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  height: 90px;
+  grid-template-columns: 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+
+</style>
+</head>
+<body>
+
+<!-- grid wrapped in inline -->
+<div class="columns" style="height: 40px">
+<div style="padding-top:2px; background:grey">
+<y>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></y></div></div>
+
+<!-- grid wrapped in inline with orthogonal writing-mode -->
+<div class="columns" style="width: 40px; height:40px">
+<div style="padding-top:2px; background:grey">
+<y style="writing-mode:vertical-lr">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></y></div></div>
+
+<!-- grid wrapped in overflow:hidden block -->
+<div class="columns" style="height: 40px; margin-top:70px">
+<div style="padding-top:2px; background:grey">
+<y style="display:block;overflow:hidden">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></y></div></div>
+
+<!-- grid wrapped in FIELDSET block -->
+<div class="columns" style="height: 40px; margin-top:70px">
+<div style="padding-top:2px; background:grey">
+<fieldset style="display:block; border:none; padding:0; margin:0">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></fieldset></div></div>
+
+<!-- grid wrapped in FIELDSET inline -->
+<div class="columns" style="height: 40px; margin-left:200px">
+<div style="padding-top:2px; background:grey">
+<fieldset style="display:inline; border:none; padding:0; margin:0">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></fieldset></div></div>
+
+<!-- grid wrapped in FIELDSET overflow:hidden block -->
+<div class="columns" style="height: 40px; margin-left:400px">
+<div style="padding-top:2px; background:grey">
+<fieldset style="display:block; overflow:hidden; border:none; padding:0; margin:0">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></fieldset></div></div>
+
+<!-- grid with orthogonal writing-mode to fragmentainer -->
+<div class="columns" style="height: 40px; margin-top:70px">
+<div style="padding-top:2px; background:grey">
+<y>
+<div class="grid" style="writing-mode:vertical-lr">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></y></div></div>
+
+<!-- vertical grid and fragmentainer with intermediary horizontal writing-mode inline -->
+<!-- XXX bug 1242660: remove the visibility:hidden DIV when we know what the rendering should be -->
+<div style="visibility:hidden">
+<div class="columns" style="width: 50px; writing-mode:vertical-lr; margin-top:70px">
+<div style="padding-top:2px; background:grey">
+<y style="writing-mode:horizontal-lr">
+<div class="grid" style="writing-mode:vertical-lr">
+<span style="grid-row:span 2"><x></x></span>
+<span><x></x></span>
+<span><x></x></span>
+</div></y></div></div>
+</div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-016-ref.html
@@ -0,0 +1,167 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of height:auto grid, not top-of-page, box-decoration-break:clone</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.block {
+  border:5px solid;
+}
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+}
+span { background:lime; border:1px solid black; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+x { display:block; height:20px; }
+br { page-break-before:always; break-before:always; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 130px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid">
+<span><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:3; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 18px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="block">
+</div></div></div>
+
+<div class="columns" style="height: 20px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="block" style="height:1px; overflow:hidden">
+</div></div></div>
+
+<div class="columns" style="height: 20px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="block" style="height:1px; overflow:hidden"></div>
+<div class="block" style="height:1px; overflow:hidden"></div>
+</div></div>
+
+<div class="columns" style="height: 100px/*fragmentainer ends in the last row*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 70px/*fragmentainer ends in the grid gap between the rows */">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 40px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 13px/*fragmentainer ends in the grid start border */; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends above the grid*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-016.html
@@ -0,0 +1,128 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of height:auto grid, not top-of-page, box-decoration-break:clone</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-016-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  box-decoration-break: clone;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 130px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 18px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+</div></div></div>
+
+<div class="columns" style="height: 20px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid" style="height:1px/*creates a Class C break opportunity at the end*/">
+</div></div></div>
+
+<div class="columns" style="height: 20px/*fragmentainer ends in the end border*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid" style="height:2px/*creates a Class C break opportunity at the end*/">
+</div></div></div>
+
+<div class="columns" style="height: 100px/*fragmentainer ends in the last row*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 70px/*fragmentainer ends in the grid gap between the rows */">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 40px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 13px/*fragmentainer ends in the grid start border */; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends above the grid*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-017-ref.html
@@ -0,0 +1,139 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation height:auto grid with first grid row at top-of-page and box-decoration-break:clone</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.block {
+  border:5px solid;
+  border-top-width:0;
+  border-bottom-width:10px;
+}
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  border-top-width:0;
+  border-bottom-width:10px;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+br { page-break-before:always; break-before:always; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 120px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid">
+<span><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:3; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="block">
+</div></div></div>
+
+<div class="columns" style="height: 10px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="block" style="height:1px;overflow:hidden"></div>
+<div class="block" style="height:1px;overflow:hidden"></div>
+</div></div>
+
+<div class="columns" style="height: 90px/*fragmentainer ends in the last row*/">
+<div style="background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<br>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 60px/*fragmentainer ends in the grid gap between the rows */">
+<div style="background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 30px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span style="background:cyan" class="t"><x></x></span>
+</div>
+<div class="grid">
+<span class="b"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:1; height:11px;"><x></x></span>
+<span class="b" style="grid-row:1; grid-column:3; height:11px; background:cyan"><x></x></span>
+<span style="grid-row:1; grid-column:1; align-self:end; background:pink"><x></x></span>
+</div></div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-017.html
@@ -0,0 +1,107 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation height:auto grid with first grid row at top-of-page and box-decoration-break:clone</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-017-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 50px;
+  grid-gap: 12px;
+  border:5px solid;
+  border-top-width:0;
+  border-bottom-width:10px;
+  box-decoration-break: clone;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 120px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 8px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid">
+</div></div></div>
+
+<div class="columns" style="height: 10px/*fragmentainer ends in the end border*/">
+<div style="background:grey">
+<div class="grid" style="height:2px/*creates a Class C break opportunity at the end*/">
+</div></div></div>
+
+<div class="columns" style="height: 90px/*fragmentainer ends in the last row*/">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 60px/*fragmentainer ends in the grid gap between the rows */">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 30px/*fragmentainer ends in the first row*/; margin-bottom:30px">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 0px/*zero height fragmentainer*/; margin-bottom:60px">
+<div style="background:grey">
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:60px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:60px"><x></x></span>
+</div></div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-018-ref.html
@@ -0,0 +1,161 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of definite height, not top-of-page, forced breaks, and box-decoration-break:clone</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*two rows would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid" style="height:60px">
+<span class="b"><x></x></span>
+<span class="b" style="grid-area:1/3; height:6px; background:cyan"><x></x></span>
+<span style="grid-area:1/3; align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:30px">
+<div style="padding-top:10px; background:grey">
+<div style="height:90px;border:5px solid;box-decoration-break: clone;"></div>
+</div></div>
+
+<div class="columns" style="height: 60px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:50px;"></div>
+<div class="grid" style="padding-bottom:20px">
+<span><x></x></span>
+</div>
+<div style="height:40px; border:5px solid;"></div>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid" style="padding-bottom:30px">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span style="align-self:end; grid-area:1/1; background:pink"><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="height:6px; background:cyan"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid" style="padding-bottom:30px">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span style="align-self:end; grid-area:1/1; background:pink"><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="height:6px; background:cyan"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:90px;"></div>
+<div class="grid" style="padding-bottom:18px">
+<span style="height:35px"><x></x></span>
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="grid-area:2/1; align-self:end; background:pink"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 97px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:87px;"></div>
+<div class="grid" style="padding-bottom:15px">
+<span style="height:35px"><x></x></span>
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="grid-area:2/1; align-self:end; background:pink"><x></x></span>
+</div>
+<div style="height:3px;border:5px solid;box-decoration-break: clone;"></div>
+</div></div>
+
+<div class="columns" style="height: 80px/*one row fits in 1st column, two in 2nd column, but forced break there*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div class="grid" style="padding-bottom:30px">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span class="b" style="background:cyan"><x></x></span>
+<span style="grid-area:1/1; align-self:end; background:pink"><x></x></span>
+</div></div>
+<div style="height:10px"></div>
+<div class="grid m" style="height:0; margin-top:1px">
+<span><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 160px/*everything would fit in 1st column*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span class="t" style="grid-row: span 2"><x></x></span>
+<span style="grid-row: span 2"><x></x></span>
+</div>
+<div style="height:48px"></div>
+<div style="height:18px; border:5px solid;">
+<span class="b" style="display:block;height:29px;width:28px"></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-018.html
@@ -0,0 +1,145 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of definite height grid, not top-of-page, forced breaks, and box-decoration-break:clone</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-018-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  height: 90px;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  box-decoration-break: clone;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+m { display:block; padding-top:10px; }
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*two rows would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:30px">
+<div style="background:grey"><m></m>
+<div class="grid break-before">
+</div></div></div>
+
+<div class="columns" style="height: 60px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span class="break-before"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span class="break-after" style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span class="break-before" style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 97px/*everything would fit in 1st column, except bottom border*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span class="break-before" style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 80px/*one row fits in 1st column, two in 2nd column, but forced break there*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span style="grid-row:3"><x></x></span>
+<span class="break-after" style="grid-row:span 2; background:cyan"><x></x></span>
+<span class="break-before" style="grid-row:2; align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 160px/*everything would fit in 1st column*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span class="break-after" style="grid-row: span 3"><x></x></span>
+<span class="break-after" style="grid-row: span 2"><x></x></span>
+</div>
+</div></div>
+
+<!-- TODO XXX bug 775628? (break-after on last row should propagate to container)
+<div class="columns" style="height: 135px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span class="break-after" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+<div style="height:20px;background:yellow"></div>
+</div></div>
+-->
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-019-ref.html
@@ -0,0 +1,150 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of height:auto grid, not top-of-page, forced break growing 'fr' row, and box-decoration-break:clone</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+  box-decoration-break: clone;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr; grid-gap:0; height:89px">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 50px; grid-gap:0;">
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr; grid-gap:0; height:89px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 50px; grid-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr; grid-gap:0; height:89px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 80px; grid-gap:0;">
+<span class="m"><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 30px; grid-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:89px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:44px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 50px; grid-row-gap:0; margin-bottom:40px;">
+<span class="m" style="height:16px; background:blue; margin: -5px 1px 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3"><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 72px; grid-row-gap:0;">
+<span class="b" style="grid-column:3"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:89px">
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:44px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+<div class="grid" style="grid-template-rows: 50px; grid-row-gap:0; margin-bottom:40px;">
+<span class="m"><x></x></span>
+<span class="m" style="height:16px; color:blue; background:blue; margin: -5px 1px 0 1px; border-width:0"></span>
+</div>
+<div class="grid" style="grid-template-rows: 72px; grid-row-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px; grid-gap:0;">
+</div>
+<div class="grid" style="grid-template-rows: 1fr; grid-gap:0; height:90px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 50px; grid-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 61px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px; grid-gap:0;">
+</div>
+<div class="grid" style="grid-template-rows: 1fr; grid-gap:0; height:62px">
+<span style="height:60px"><x></x></span>
+<span style="height:50px"><i style="height:54px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 0; grid-gap:0; border-width:0 5px">
+<span class=m style="grid-column:2; border-width:0 1px; height:0"><i style="height:6px;margin:0"></i></span>
+<span class=b style="grid-column:3; height:0"></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-019.html
@@ -0,0 +1,115 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of height:auto grid, not top-of-page, forced break growing 'fr' row, and box-decoration-break:clone</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-019-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+  box-decoration-break: clone;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 1fr 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px 1fr 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px 1fr 50px;">
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow row 2*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px 1fr 50px; grid-gap:0;">
+<span style="grid-row:2/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 61px/*trigger OVERFLOW_INCOMPLETE for the item*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px 1fr; grid-gap:0;">
+<span style="grid-row:2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-020-ref.html
@@ -0,0 +1,208 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation with forced break propagation</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+.no-border { border-style:none; }
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px;
+  grid-auto-rows: 10px;
+  grid-gap: 2px;
+  border:5px solid;
+  height: 20px; /* create Class C break opportunities at both ends */
+  align-content: center;
+}
+.start {
+  align-content: start;
+}
+
+span { background:lime; border:1px solid black; }
+.bb { border-bottom-width:6px; }
+x { display:block; height: 40px; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m {  border:5px solid; border-top-width:0; border-bottom-width:0; }
+.br1 { height:34px; border-width:5px; border-top-style:solid; }
+.br2 { height:4px; }
+.br3 { height:39px; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid start">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="br1"></div>
+<div class="grid b">
+<span class="avoid-break"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid start">
+<span class="avoid-break"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="padding-top:1px; background:grey">
+<div class="br3"></div>
+<div class="grid">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="padding-top:1px; background:grey">
+<div class="br3"></div>
+<div class="grid start">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="padding-top:1px; background:grey">
+<div class="br1"></div>
+<div class="grid b">
+<span class="avoid-break"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="padding-top:1px; background:grey">
+<div class="grid start">
+<span class="avoid-break"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:16px">
+<div style="background:grey">
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:16px">
+<div style="padding-top:1px; background:grey">
+<div class="br2"></div>
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:10px">
+<div style="background:grey">
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:10px">
+<div style="padding-top:1px; background:grey">
+<div class="br2"></div>
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:0px">
+<div style="background:grey">
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:0px; margin-top:20px">
+<div style="background:grey">
+<div style="height:1px; overflow:hidden"></div>
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div style="height:1px; overflow:hidden"></div>
+<div style="height:5px; overflow:hidden; background:black; "></div>
+<div class="grid m" style="height:10px;grid-auto-rows: 0px; align-content:start;">
+<span class="bb"></span>
+</div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div style="">
+<div style="height:1px; overflow:hidden"></div>
+<div style="height:5px; overflow:hidden; background:black; "></div>
+</div>
+<div style="height:7px; width:30px; margin-left:5px; overflow:hidden; background:black;"></div>
+<div class="grid m" style="height:10px;grid-auto-rows: 0px; align-content:start;">
+<span class="bb"></span>
+</div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div style="height:1px; overflow:hidden; position:relative"></div>
+<div style="border:5px solid; height:1px; overflow:hidden; ">
+<div style="height:7px; width:30px; overflow:hidden;  position:absolute; background:black;"></div>
+</div>
+</div>
+</div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div style="padding-top:1px; ">
+<div style="height:1px; overflow:hidden"></div>
+<div class="grid" style="height:1px;grid-auto-rows: 1px;">
+<span class="break-before bb"></span>
+<span class="break-before bb"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div style="padding-top:1px; ">
+<div style="height:1px; overflow:hidden"></div>
+<div class="grid" style="height:1px;grid-auto-rows: 11px;">
+<span class="break-before bb"></span>
+<span class="break-before bb"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div style="padding-top:1px; ">
+<div style="height:1px; overflow:hidden"></div>
+<div class="grid" style="height:1px;grid-auto-rows: 11px;">
+<span class="break-before bb" style="grid-row:span 2"></span>
+<span class="break-before bb"></span>
+</div></div></div>
+
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div style="padding-top:1px; ">
+<div style="height:1px; overflow:hidden"></div>
+<div class="grid" style="height:1px;grid-auto-rows: 11px;">
+<span class="break-before bb"></span>
+<span class="break-before bb" style="grid-row:span 2"></span>
+</div></div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-020.html
@@ -0,0 +1,215 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation with forced break propagation</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-020-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+.no-border { border-style:none; }
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px;
+  grid-auto-rows: 10px;
+  grid-gap: 2px;
+  border:5px solid;
+  height: 20px; /* create Class C break opportunities at both ends */
+  align-content: center;
+}
+.start {
+  align-content: start;
+}
+
+span { background:lime; border:1px solid black; }
+.bb { border-bottom-width:6px; }
+x { display:block; height: 40px; }
+m { display:block; padding-top:1px; }
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid start">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid">
+<span class="avoid-break"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid start">
+<span class="avoid-break"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey"><m></m>
+<div class="grid start">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span class="avoid-break"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey"><m></m>
+<div class="grid start">
+<span class="avoid-break"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:16px">
+<div style="background:grey">
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:16px">
+<div style="background:grey"><m></m>
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:10px">
+<div style="background:grey">
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:10px">
+<div style="background:grey"><m></m>
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:0px">
+<div style="background:grey">
+<div class="grid" style="height:10px">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns" style="height:0px; margin-top:20px">
+<div style="background:grey"><m></m>
+<div class="grid" style="height:10px;">
+<span class="break-before"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div><m></m>
+<div class="grid" style="height:10px;grid-auto-rows: 0px;">
+<span class="break-before bb"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div><m></m>
+<div class="grid" style="height:10px;grid-auto-rows: 0px;">
+<span class="break-before bb"></span>
+<span class="break-before bb"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div><m></m>
+<div class="grid" style="height:1px;grid-auto-rows: 1px;">
+<span class="break-before bb"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div><m></m>
+<div class="grid" style="height:1px;grid-auto-rows: 1px;">
+<span class="break-before bb"></span>
+<span class="break-before bb"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div><m></m>
+<div class="grid" style="height:1px;grid-auto-rows: 11px;">
+<span class="break-before bb"></span>
+<span class="break-before bb"></span>
+</div></div></div>
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div><m></m>
+<div class="grid" style="height:1px;grid-auto-rows: 11px;">
+<span class="break-before bb" style="grid-row:span 2"></span>
+<span class="break-before bb"></span>
+</div></div></div>
+
+
+<div class="columns no-border" style="height:0px; margin-top:20px">
+<div><m></m>
+<div class="grid" style="height:1px;grid-auto-rows: 11px;">
+<span class="break-before bb"></span>
+<span class="break-before bb" style="grid-row:span 2"></span>
+</div></div></div>
+
+<!--
+
+XXX TODO: propagation of break-after on the last row to the container doesn't work.
+XXX TODO: I'm guessing the block frame code doesn't know how to deal with that b/c
+XXX TODO: it expects the frame constructor to have created a nsPageBreakFrame...
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid">
+<span class="break-after"></span>
+</div>
+<div style="border-top:2px solid blue"></div>
+</div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid">
+<img src="data:image/gif;base64,R0lGODlhAQABAIABAAD/AP///ywAAAAAAQABAAACAkQBADs=" class="break-after"></button>
+</div>
+<div style="border-top:2px solid blue"></div>
+</div></div>
+
+-->
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-021-ref.html
@@ -0,0 +1,188 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation with ::before/::after items</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 3;
+      -ms-columns: 3;
+  -webkit-columns: 3;
+          columns: 3;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 1px;
+  height: 150px;
+}
+.no-border { border-style:none; }
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px;
+  grid-auto-rows: 20px;
+  grid-gap: 2px;
+  border:5px solid;
+  counter-reset: item;
+}
+.start {
+  align-content: start;
+}
+
+span { counter-increment:item; }
+.br1.before { grid-row:1; }
+.ar1.after { grid-row:1; }
+.br2.before { grid-row:2; }
+.ar2.after { grid-row:2; }
+.br7.before { grid-row:7; }
+.ar7.after { grid-row:7; }
+
+.span5 { grid-row-end: span 5; background:lime; }
+
+.span15 { grid-row: 1 / span 15; grid-column:1; background:lime; }
+.span15.before { grid-row-end: span 15; grid-column:3; background:grey; }
+.span15.after { grid-row: 2 / span 15; grid-column:2; background:lime; }
+
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+</style>
+</head>
+<body>
+
+<div class="columns">
+<div class="grid">
+<span><c>5:before</c></span>
+<span><c>2:after</c></span>
+<span><c>1:before</c></span>
+<span class="ar2"><c>1</c></span>
+<span class="ar2"><c>1:after</c></span>
+<span class="ar2"><c>2:before</c></span>
+<span><c>2</c></span>
+<span><c>3:before</c></span>
+<span><c>3</c></span>
+<span><c>3:after</c></span>
+<span><c>4:before</c></span>
+<span><c>4</c></span>
+<span class="br1"><c>4:after</c></span>
+<span class="br1"><c>5</c></span>
+<span class="br1"><c>5:after</c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c>5:after</c></span>
+<span><c>4:after</c></span>
+<span><c>1:before</c></span>
+<span><c>1</c></span>
+<span><c>1:after</c></span>
+<span><c>2:before</c></span>
+<span><c>2</c></span>
+<span><c>2:after</c></span>
+<span><c>3:before</c></span>
+<span class="ar2"><c>3</c></span>
+<span class="ar2"><c>3:after</c></span>
+<span class="ar2"><c>4:before</c></span>
+<span class="ar1"><c>4</c></span>
+<span class="ar1"><c>5:before</c></span>
+<span class="ar1"><c>5</c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c>5:after</c></span>
+<span><c>5:before</c></span>
+<span><c>1:before</c></span>
+<span><c>1</c></span>
+<span><c>1:after</c></span>
+<span><c>2:before</c></span>
+<span><c>2</c></span>
+<span><c>2:after</c></span>
+<span><c>3:before</c></span>
+<span><c>3</c></span>
+<span><c>3:after</c></span>
+<span><c>4:before</c></span>
+<span class="ar1 br2"><c>4</c></span>
+<span class="ar1 br2"><c>4:after</c></span>
+<span class="ar1 br2"><c>5</c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c>5:before</c></span>
+<span><c>5:after</c></span>
+<span><c>1:before</c></span>
+<span><c>1</c></span>
+<span><c>1:after</c></span>
+<span><c>2:before</c></span>
+<span><c>2</c></span>
+<span><c>2:after</c></span>
+<span><c>3:before</c></span>
+<span><c>3</c></span>
+<span><c>3:after</c></span>
+<span><c>4:before</c></span>
+<span class="ar2 br1"><c>4</c></span>
+<span class="ar2 br1"><c>4:after</c></span>
+<span class="ar2 br1"><c>5</c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c>5:before</c></span>
+<span><c>4:before</c></span>
+<span><c>1:before</c></span>
+<span><c>1</c></span>
+<span><c>1:after</c></span>
+<span><c>2:before</c></span>
+<span><c>2</c></span>
+<span><c>2:after</c></span>
+<span><c>3:before</c></span>
+<span class="br2"><c>3</c></span>
+<span class="br2"><c>3:after</c></span>
+<span class="br2"><c>4</c></span>
+<span class="br1"><c>4:after</c></span>
+<span class="br1"><c>5</c></span>
+<span class="br1"><c>5:after</c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c>1:before</c></span>
+<span><c>5:before</c></span>
+<span><c>1</c></span>
+<span><c>1:after</c></span>
+<span><c>2:before</c></span>
+<span><c>2</c></span>
+<span><c>4:before</c></span>
+<span><c>2:after</c></span>
+<span class="span5"><c>3:before</c></span>
+<span class="span5"><c>3</c></span>
+<span class="span5"><c></c></span>
+<span class="br7"><c></c></span>
+<span class="br2"><c></c></span>
+<span class="br2"><c></c></span>
+<span class="br2"><c></c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid" style="grid-template-columns: 30px 30px 30px">
+<span class="span15 before"><c>1:before</c></span>
+<span class="span15"><c>1</c></span>
+<span class="span15 after"><c>1:after</c></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-021.html
@@ -0,0 +1,133 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation with ::before/::after items</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-021-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 3;
+      -ms-columns: 3;
+  -webkit-columns: 3;
+          columns: 3;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 1px;
+  height: 150px;
+}
+.no-border { border-style:none; }
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px;
+  grid-auto-rows: 20px;
+  grid-gap: 2px;
+  border:5px solid;
+  counter-reset: item;
+}
+.start {
+  align-content: start;
+}
+
+span { display:contents; }
+span::before { counter-increment:item; content: counter(item) ":before"; }
+span::after { content: counter(item) ":after"; }
+c::before { content: counter(item); }
+.br1::before { grid-row:1; }
+.ar1::after { grid-row:1; }
+.br2::before { grid-row:2; }
+.ar2::after { grid-row:2; }
+.br7::before { grid-row:7; }
+.ar7::after { grid-row:7; }
+
+.span5 * { grid-row-end: span 5; background:lime; }
+.span5::before { grid-row-end: span 5; background:lime; }
+.span5::after { grid-row-end: span 5; background:lime; }
+
+.span15 * { grid-row: 1 / span 15; background:lime; }
+.span15::before { grid-row-end: span 15; background:grey; }
+.span15::after { grid-row: 2 / span 15; background:lime; }
+
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+</style>
+</head>
+<body>
+
+<div class="columns">
+<div class="grid">
+<span><c></c></span>
+<span class="ar2"><c></c></span>
+<span><c></c></span>
+<span><c></c></span>
+<span class="br1"><c></c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c></c></span>
+<span><c></c></span>
+<span><c></c></span>
+<span class="ar2"><c></c></span>
+<span class="ar1"><c></c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c></c></span>
+<span><c></c></span>
+<span><c></c></span>
+<span><c></c></span>
+<span class="ar1 br2"><c></c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c></c></span>
+<span><c></c></span>
+<span><c></c></span>
+<span><c></c></span>
+<span class="ar2 br1"><c></c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c></c></span>
+<span><c></c></span>
+<span><c></c></span>
+<span class="br2"><c></c></span>
+<span class="br1"><c></c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid">
+<span><c></c></span>
+<span><c></c></span>
+<span class="span5"><c></c></span>
+<span class="br7"><c></c></span>
+<span class="br2"><c></c></span>
+</div></div>
+
+<div class="columns">
+<div class="grid" style="grid-template-columns: 30px 30px 30px">
+<span class="span15"><c></c></span>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-022.html
@@ -0,0 +1,104 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of height:auto grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-007-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow row 2*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px min-content 50px; grid-gap:0;">
+<span style="grid-row:2/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-023-ref.html
@@ -0,0 +1,138 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of definite height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0; height:86px">
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0; height:86px">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 80px; grid-gap:0; padding-bottom:6px">
+<span class="m"><x></x></span>
+</div></div>
+<div style="height:9px"></div>
+<div class="grid" style="align-content: start; grid-gap:0; height:1px; border-width:0; margin-left:5px">
+<span class="b"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 86px; grid-row-gap:0;">
+<span class="m" style="height:10px; background:blue; margin: 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3; height:92px;"><x></x></span>
+</div></div>
+<div style="height:9px"></div>
+<div class="grid" style="grid-template-rows: auto; grid-row-gap:0; height:1px; border-width:0; margin-left:5px;">
+<span class="b" style="grid-column:3; height:29px"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:50px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+<div class="grid b" style="grid-template-rows: 86px; grid-row-gap:0;">
+<span class="m" style="height:92px"><x></x></span>
+<span class="m" style="height:11px; color:blue; background:blue; margin: 0 1px; border-width:0"></span>
+</div></div>
+<div style="height:9px"></div>
+<div class="grid" style="grid-template-rows: 0; grid-row-gap:0; height:1px; border-width:0; margin-left:5px;">
+<span class="b" style="height:29px"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 50px; grid-gap:0;">
+</div>
+<div class="grid m" style="grid-template-rows: 1fr; grid-gap:0; height:100px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0; height:30px;">
+<span class="b" style="height:49px"><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>
+

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-023.html
@@ -0,0 +1,105 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of definite height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-023-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  height: 180px;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow row 2*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px min-content 50px; grid-gap:0;">
+<span style="grid-row:2/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-024-ref.html
@@ -0,0 +1,172 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of a height:auto  definite max-height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0; height:50px">
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0; height:50px">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 80px; grid-gap:0;">
+<span class="m"><x></x></span>
+</div>
+<div style="height:20px"></div>
+<div class="grid b" style="grid-gap:0; height:6px">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 92px; grid-row-gap:0; height:86px">
+<span class="m" style="height:10px; background:blue; margin: 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3"><x></x></span>
+</div></div>
+<div style="height:9px"></div>
+<div class="grid" style="grid-template-rows: auto; grid-row-gap:0; height:1px; border-width:0; margin-left:5px;">
+<span class="b" style="grid-column:3; height:29px"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:50px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+<div class="grid b" style="grid-template-rows: 92px; grid-row-gap:0; height:86px">
+<span class="m"><x></x></span>
+<span class="m" style="height:11px; color:blue; background:blue; margin: 0 1px; border-width:0"></span>
+</div></div>
+<div style="height:9px"></div>
+<div class="grid" style="grid-template-rows: auto; grid-row-gap:0; height:1px; border-width:0; margin-left:5px;">
+<span class="b" style="height:29px"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 50px; grid-gap:0;">
+</div>
+<div class="grid m" style="grid-template-rows: 1fr; grid-gap:0; height:100px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0; height:30px;">
+<span class="b" style="height:49px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 80px; grid-gap:0;">
+<span class="m"><x></x></span>
+</div>
+<div style="height:20px"></div>
+<div class="grid b" style="grid-gap:0; height:6px">
+<span class="b"><x></x></span>
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 92px; grid-row-gap:0; height:86px">
+<span class="m" style="height:10px; background:blue; margin: 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3"><x></x></span>
+</div></div>
+<div style="height:9px"></div>
+<div class="grid m" style="border-style:none; margin-left:5px">
+<span><x></x></span>
+<span class="b" style="grid-column:3; height:29px"><x></x></span>
+</div>
+</div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-024.html
@@ -0,0 +1,126 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of a height:auto  definite max-height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-024-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  max-height: 180px;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow row 2*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px min-content 50px; grid-gap:0;">
+<span style="grid-row:2/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+<span style="grid-row:4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:5"><x></x></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-025-ref.html
@@ -0,0 +1,177 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of a height:auto, small definite max-height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px; grid-gap:0; height:20px">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div></div>
+<div style="height:69px"></div>
+<div class="grid" style="grid-template-rows: 50px; border-style:none; margin-left:5px">
+<span><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px; grid-gap:0; height:20px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div></div>
+<div style="height:69px"></div>
+<div class="grid" style="grid-template-rows: 50px; border-style:none; margin-left:5px">
+<span class="b"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px; grid-gap:0; height:20px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div></div>
+<div class="grid m" style="grid-template-rows: 80px; border-style:none; margin-left:5px">
+<span class="m"><x></x></span>
+</div>
+<div style="height:20px"></div>
+<div class="grid b" style="border-style:none; margin-left:5px">
+<span class="b"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 17px 77px; grid-row-gap:0; height:20px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div></div>
+<div class="grid" style="grid-template-rows: 92px; grid-row-gap:0; height:86px; border-style:none; margin-left:5px">
+<span class="m" style="height:10px; background:blue; margin: 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3"><x></x></span>
+</div>
+<div style="height:9px"></div>
+<div class="grid" style="grid-template-rows: auto; border-style:none; margin-left:5px">
+<span class="b" style="grid-column:3; height:29px"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 17px 77px; grid-row-gap:0; height:20px">
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:50px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div></div>
+<div class="grid" style="grid-template-rows: 92px; grid-row-gap:0; height:86px; border-style:none; margin-left:5px">
+<span class="m"><x></x></span>
+<span class="m" style="height:11px; color:blue; background:blue; margin: 0 1px; border-width:0"></span>
+</div>
+<div style="height:9px"></div>
+<div class="grid" style="grid-template-rows: auto; border-style:none; margin-left:5px">
+<span class="b" style="height:29px"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px; grid-gap:0; height:20px">
+</div></div>
+<div style="height:69px"></div>
+<div class="grid" style="grid-template-rows: 100px; grid-gap:0; border-style:none; margin-left:5px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid" style="grid-template-rows: 50px; border-style:none; margin-left:5px">
+<span class="b" style="height:49px"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px; grid-gap:0; height:20px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div></div>
+<div style="height:69px"></div>
+<div class="grid" style="grid-template-rows: 80px; border-style:none; margin-left:5px">
+<span class="m"><x></x></span>
+</div>
+<div style="height:20px"></div>
+<div class="grid" style="grid-gap:0; border-style:none; margin-left:5px">
+<span class="b"><x></x></span>
+<span><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 17px 77px; grid-row-gap:0; height:20px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div></div>
+<div style="height:69px"></div>
+<div class="grid" style="grid-template-rows: 92px; grid-row-gap:0; height:86px; border-style:none; margin-left:5px">
+<span class="m" style="height:10px; background:blue; margin: 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3"><x></x></span>
+</div>
+<div style="height:9px"></div>
+<div class="grid" style="border-style:none; margin-left:5px">
+<span><x></x></span>
+<span class="b" style="grid-column:3; height:29px"><x></x></span>
+</div>
+</div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-025.html
@@ -0,0 +1,126 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of a height:auto, small definite max-height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-025-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  max-height: 20px;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow row 2*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px min-content 50px; grid-gap:0;">
+<span style="grid-row:2/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+<span style="grid-row:4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:5"><x></x></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-026-ref.html
@@ -0,0 +1,166 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of definite height grid, forced row breaks, avoid-break grid</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+s { display:block; height:90px; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*two rows would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<s></s>
+<div class="grid t">
+<span><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b" style="height:60px">
+<span class="b"><x></x></span>
+<span class="b" style="grid-area:1/3; height:6px; background:cyan"><x></x></span>
+<span style="grid-area:1/3; align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:30px">
+<div style="padding-top:10px; background:grey">
+<s style="height:20px;"></s>
+<div style="height:90px;border:5px solid;"></div>
+</div></div>
+
+<div class="columns" style="height: 60px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:50px;"></div>
+<div class="grid t">
+<span><x></x></span>
+</div>
+<div style="height:60px; border:5px solid; border-top-width:0;">
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<s></s>
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b" style="padding-bottom:30px">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span style="align-self:end; grid-area:1/1; background:pink"><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="height:6px; background:cyan"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<s></s>
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div style="height:40px;"></div>
+<div class="grid b" style="padding-bottom:30px">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span style="align-self:end; grid-area:1/1; background:pink"><x></x></span>
+<span class="b"><x></x></span>
+<span class="b" style="height:6px; background:cyan"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:90px;"></div>
+<div class="grid" style="padding-bottom:18px">
+<span style="height:35px"><x></x></span>
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="grid-area:2/1; align-self:end; background:pink"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 97px/*everything would fit in 1st column, except bottom border*/">
+<div style="padding-top:10px; background:grey">
+<div style="height:87px;"></div>
+<div class="grid t" style="padding-bottom:18px">
+<span style="height:35px"><x></x></span>
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="grid-area:2/1; align-self:end; background:pink"><x></x></span>
+</div>
+<div class="grid b"></div>
+</div></div>
+
+<div class="columns" style="height: 80px/*one row fits in 1st column, two in 2nd column, but forced break there*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid t">
+<span class="t"><x></x></span>
+<span class="t" style="background:cyan"><x></x></span>
+</div>
+<div class="grid m">
+<span class="b" style="grid-area:1/1; height:6px"><x></x></span>
+<span class="b" style="background:cyan"><x></x></span>
+<span style="grid-area:1/1; align-self:end; background:pink"><x></x></span>
+</div>
+<div style="height:50px"></div>
+<div class="grid b">
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 160px/*everything would fit in 1st column*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid t">
+<span class="t" style="grid-row: span 2"><x></x></span>
+<span style="grid-row: span 2"><x></x></span>
+</div>
+<div style="height:53px"></div>
+<div style="height:18px; border:5px solid; border-top-width:0;">
+<span class="b" style="display:block;height:29px;width:28px"></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-026.html
@@ -0,0 +1,134 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of definite height grid, forced row breaks, avoid-break grid</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-026-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  height: 90px;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+
+  page-break-inside:avoid;
+  break-inside:avoid;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+m { display:block; padding-top:10px; }
+.break-before { page-break-before:always; break-before:always; }
+.break-after { page-break-after:always; break-after:always; }
+
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*two rows would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1"><x></x></span>
+<span><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height:30px">
+<div style="background:grey"><m></m>
+<div class="grid break-before">
+</div></div></div>
+
+<div class="columns" style="height: 60px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span class="break-before"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span class="break-before" style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div></div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span class="break-after" style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*everything would fit in 1st column*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span class="break-before" style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 97px/*everything would fit in 1st column, except bottom border*/">
+<div style="background:grey"><m></m>
+<div class="grid">
+<span style="grid-row:span 2"><x></x></span>
+<span style="height:35px; background:cyan"><x></x></span>
+<span style="align-self:end; background:pink"><x></x></span>
+<span class="break-before" style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 80px/*one row fits in 1st column, two in 2nd column, but forced break there*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span style="grid-row:3"><x></x></span>
+<span class="break-after" style="grid-row:span 2; background:cyan"><x></x></span>
+<span class="break-before" style="grid-row:2; align-self:end; background:pink"><x></x></span>
+<span style="grid-row:1; height:35px"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 160px/*everything would fit in 1st column*/">
+<div style="padding-top:30px; background:grey">
+<div class="grid">
+<span class="break-after" style="grid-row: span 3"><x></x></span>
+<span class="break-after" style="grid-row: span 2"><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-027.html
@@ -0,0 +1,127 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of a height:auto, small definite min/max-height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-025-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  max-height: 10px;
+  min-height: 20px;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow row 2*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px min-content 50px; grid-gap:0;">
+<span style="grid-row:2/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+<span style="grid-row:4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px;">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:5"><x></x></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-028-ref.html
@@ -0,0 +1,174 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of a height:auto, small definite min-height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: space-evenly;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-top-width:0; border-bottom-width:0; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0;">
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 50px; grid-gap:0; height:100px">
+<span class="b"><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 50px; grid-gap:0; height:100px">
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0; height:6px">
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 80px; grid-gap:0;">
+<span class="m"><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 30px; grid-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 92px; grid-row-gap:0;">
+<span class="m" style="height:10px; background:blue; margin: 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3"><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 30px; grid-row-gap:0;">
+<span class="b" style="grid-column:3"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:50px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+<div class="grid b" style="grid-template-rows: 92px; grid-row-gap:0; align-content:start; height:26px;">
+<span class="m"><x></x></span>
+<span class="m" style="height:11px; color:blue; background:blue; margin: 0 1px; border-width:0"></span>
+</div></div>
+<div style="height:69px"></div>
+<div class="grid" style="grid-template-rows: 30px; grid-row-gap:0; align-content:start; height:1px; border-width:0; margin-left:5px;">
+<span class="b"><x></x></span>
+</div>
+</div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 50px; grid-gap:0;">
+</div>
+<div class="grid m" style="grid-template-rows: 1fr; grid-gap:0; height:100px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid b" style="grid-template-rows: 50px; grid-gap:0;">
+<span class="b"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 1fr; grid-gap:0; height:94px">
+<span class="t"><x></x></span>
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span style="height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 80px; grid-gap:0;">
+<span class="m"><x></x></span>
+</div>
+<div style="height:20px"></div>
+<div class="grid b" style="grid-gap:0;">
+<span class="b"><x></x></span>
+<span><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 17px 1fr; grid-row-gap:0; height:94px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span class="t" style="grid-row:1/span 2"><x></x></span>
+</div>
+<div class="grid m" style="grid-template-rows: 92px; grid-row-gap:0; height:92px">
+<span class="m" style="height:10px; background:blue; margin: 0 1px; border-width:0"><x></x></span>
+<span class="m" style="grid-column:3"><x></x></span>
+</div>
+<div style="height:8px"></div>
+<div class="grid b" style="">
+<span><x></x></span>
+<span class="b" style="grid-column:3; height:29px"><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-028.html
@@ -0,0 +1,125 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of a height:auto, small definite min-height grid, forced break growing min-content row</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-028-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  min-height: 20px;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0; min-height:300px">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 2"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0; min-height:120px">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px; min-height:120px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px; min-height:120px; max-height:100px">
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow row 2*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 50px min-content 50px; grid-gap:0; min-height:120px">
+<span style="grid-row:2/span 2"><x></x></span>
+<span style="grid-row:2; height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><i></i><i></i><i></i><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 50px; grid-gap:0;">
+<span style="height:50px"><i style="height:60px"></i><x></x></span>
+<span class="avoid-break" style="height:60px"><i></i><i></i><i></i><x></x></span>
+<span style="grid-row:1/span 4"><x></x></span>
+<span style="grid-row:4"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 5px min-content 50px; min-height:200px">
+<span style="grid-row:2; height:50px"><x></x><i style="height:60px"></i></span>
+<span class="avoid-break" style="grid-row:2; height:60px"><x></x><i></i><i></i><i></i></span>
+<span style="grid-row:1/span 5"><x></x></span>
+<span style="grid-row:5"><x></x></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-029-ref.html
@@ -0,0 +1,207 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation, various edge cases</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: block;
+  border:5px solid;
+  align-content: start;
+}
+span { display:block; height:20px; width:30px; }
+i { display:block; height:10px; background:blue; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-bottom-width:0; border-top-width:0; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height:30px">
+<div style="background:grey">
+<div class="grid t" style="height:25px">
+<span><i style="height:25px"></i></span>
+</div>
+<div class="grid m" style="height:25px">
+<span><i style="height:25px"></i></span>
+</div>
+<div class="grid m" style="height:25px">
+<span><i style="height:10px"></i></span>
+</div>
+<div class="grid b" style="height:25px">
+</div>
+</div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid t" style="height:60px; overflow:hidden">
+<span><i style="overflow:hidden;height:60px"></i></span>
+</div>
+<div class="grid m" style="height:40px">
+<span><i style="height:20px"></i></span>
+</div>
+<div class="grid b" style="height:0px">
+</div>
+</div></div>
+
+<div class="columns" style="height:30px; margin-left:40px">
+<div style="background:grey">
+<div class="grid t" style="height:25px">
+<span><i style="height:25px"></i></span>
+</div>
+<div class="grid m" style="height:25px">
+<span><i style="height:25px"></i></span>
+</div>
+<div class="grid m" style="height:25px">
+<span><i style="height:10px"></i></span>
+</div>
+<div class="grid b" style="height:25px">
+</div>
+</div></div>
+
+<div class="columns" style="height:40px; margin-left:40px">
+<div style="background:grey">
+<div class="grid t" style="height:60px; overflow:hidden">
+<span><i style="overflow:hidden;height:60px"></i></span>
+</div>
+<div class="grid m" style="height:40px">
+<span><i style="height:20px"></i></span>
+</div>
+<div class="grid b" style="height:0px">
+</div>
+</div></div>
+
+<div class="columns" style="height:40px; margin-left:80px">
+<div style="background:grey">
+<div class="grid" style="height:20px">
+<span><i style="overflow:hidden;height:60px"></i></span>
+</div></div>
+<div style="height:10px"></div>
+<div style="margin-left:5px">
+<span><i style="height:20px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px; margin-left:120px">
+<div style="background:grey">
+<div class="grid t" style="height:30px">
+<span><i style="height:30px"></i></span>
+</div>
+<div style="height:35px"></div>
+<div class="grid b" style="height:30px">
+<span><i style="height:50px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid t" style="height:30px">
+<span><i style="height:30px"></i></span>
+</div>
+<div style="height:35px"></div>
+<div class="grid b" style="height:32px">
+<span><i style="height:50px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid t" style="height:45px">
+<span style="height:45px"><i style="height:45px"></i></span>
+</div>
+<div style="height:20px"></div>
+<div class="grid b" style="height:16px">
+<span style="height:16px"><i style="height:35px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid t" style="height:65px">
+<span style="height:65px"><i style="height:65px"></i></span>
+</div>
+<div class="grid b" style="height:0px">
+<span><i style="height:15px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid t" style="height:60px">
+<span style="height:60px"><i style="height:60px"></i></span>
+</div>
+<div style="height:5px"></div>
+<div class="grid b" style="height:1px">
+<span><i style="height:20px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid t" style="height:61px">
+<span style="height:62px"><i style="height:62px"></i></span>
+</div>
+<div style="height:4px"></div>
+<div class="grid b" style="height:0px">
+<span><i style="height:18px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div style="overflow:hidden">
+<div class="grid" style="height:32px;">
+<span><i style="height:33px;"></i></span>
+</div>
+</div>
+<div class="grid m" style="height:0px">
+<span><i style="height:40px"></i></span>
+</div></div>
+<div style="height:40px"></div>
+<div class="grid m" style="height:0px">
+<span><i style="height:7px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div style="overflow:hidden">
+<div class="grid" style="height:32px;">
+<span><i style="height:33px;"></i></span>
+</div>
+</div>
+<div class="grid m" style="height:0px">
+<span><i style="height:40px"></i></span>
+</div></div>
+<div style="height:40px"></div>
+<div class="grid m" style="height:0px">
+<span><i style="height:7px"></i></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-029.html
@@ -0,0 +1,141 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation, various edge cases</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-029-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 30px 30px 30px;
+  grid-auto-rows: 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; height:20px; }
+x { display:block; height:20px;}
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height:30px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 5px; min-height:100px">
+<span><i style="height:60px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 60px; min-height:100px">
+<span><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:30px; margin-left:40px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 5px; height:100px; min-height:100px">
+<span><i style="height:60px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:40px; margin-left:40px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 60px; height:20px; min-height:100px">
+<span><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:40px; margin-left:80px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 60px; height:20px;">
+<span><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px; margin-left:120px">
+<div style="background:grey">
+<div class="grid" style="grid-gap:2px; min-height:50px">
+<span style="grid-row:span 2"><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid" style="grid-gap:2px; height:62px">
+<span style="grid-row:span 2"><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 30px 15px 16px; grid-gap:0; height:61px">
+<span style="grid-row:span 2; height:auto"><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 30px 35px 0px; grid-gap:0; height:61px">
+<span style="grid-row:span 2; height:auto"><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 30px 30px 1px; grid-gap:0; height:61px">
+<span style="grid-row:span 2; height:auto"><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:70px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 30px 30px 2px 10px; grid-gap:0; height:61px">
+<span style="grid-row:span 3; height:auto"><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 33px 30px; max-height:32px;">
+<span><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+<div class="columns" style="height:40px">
+<div style="background:grey">
+<div class="grid" style="grid-template-rows: 33px 30px; min-height:32px; max-height:0px;">
+<span><i style="height:80px"></i></span>
+</div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-030-ref.html
@@ -0,0 +1,111 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation of a height:auto, growing min-content row that makes the grid container break</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  max-height: 20px;
+  grid-template-columns: 30px 30px 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0; max-height:90px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0; max-height:89px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0; max-height:94px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0; max-height:95px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0; max-height:200px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0; max-height:none;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-030.html
@@ -0,0 +1,114 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation of a height:auto, growing min-content row that makes the grid container break</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-030-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  max-height: 20px;
+  grid-template-columns: 30px 30px 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; max-height:90px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; max-height:89px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; max-height:94px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; max-height:95px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; max-height:200px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; max-height:none;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-031-ref.html
@@ -0,0 +1,115 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Reference: Fragmentation with specified grid height, growing min-content row that makes the grid container break</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  max-height: 20px;
+  grid-template-columns: 30px 30px 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.t { border-bottom-width:0; }
+.b { border-top-width:0; }
+.m { border-bottom-width:0; border-top-width:0; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 94px; grid-gap:0; height:90px; max-height:90px; ">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+</div>
+<div style="height:4px"></div>
+<div class="grid b" style="height:0px;grid-template-rows: 22px;"><span></span></div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0; max-height:89px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 94px; grid-gap:0; height:94px; max-height:94px; ">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+</div>
+<div class="grid b" style="height:0px;grid-template-rows: 22px;"><span></span></div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0; max-height:95px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: 94px 10px; grid-gap:0;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid t" style="grid-template-rows: 94px; grid-gap:0; height:90px; max-height:90px; ">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+</div>
+<div style="height:4px"></div>
+<div class="grid b" style="height:0px;grid-template-rows: 10px;"><span></span></div>
+</div></div>
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-031.html
@@ -0,0 +1,114 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: Fragmentation with specified grid height, growing min-content row that makes the grid container break</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-031-ref.html">
+  <style type="text/css">
+html,body {
+    color:black; background-color:white; font-size:16px; padding:0; margin:0;
+}
+body { overflow:hidden; }
+
+.columns {
+  position:relative;
+     -moz-columns: 5;
+      -ms-columns: 5;
+  -webkit-columns: 5;
+          columns: 5;
+     -moz-column-fill: auto;
+      -ms-column-fill: auto;
+  -webkit-column-fill: auto;
+          column-fill: auto;
+  border: 2px dashed;
+  margin-bottom: 5px;
+}
+
+.grid {
+  display: grid;
+  height: 20px;
+  grid-template-columns: 30px 30px 30px;
+  grid-gap: 12px;
+  border:5px solid;
+  align-content: start;
+}
+span { background:lime; border:1px solid black; }
+x { display:block; height:20px; }
+.avoid-break { page-break-inside:avoid; break-inside:avoid; }
+
+i { display:block; height:10px; margin-top:7px; background:blue; }
+</style>
+</head>
+<body>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; height:90px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; height:89px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; height:94px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; height:95px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; max-height:50px;">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"><x></x></span>
+</div>
+</div></div>
+
+<div class="columns" style="height: 100px/*trigger NS_INLINE_IS_BREAK_BEFORE for the item: grow the row*/">
+<div style="padding-top:1px; background:grey">
+<div class="grid" style="grid-template-rows: min-content 10px; grid-gap:0; min-height:90px">
+<span></span>
+<span class="avoid-break" style="height:60px"><i></i><x></x><i></i><x></x><i></i><x></x></span>
+<span style="grid-row:2;"></span>
+</div>
+</div></div>
+
+
+</body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-dyn1-002.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html class="reftest-wait"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: test 002 dynamic remove/insert first item</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-002-ref.html">
+
+<script src="support/dyn.js"></script>
+<script>
+function runTest(text) {
+  document.body.innerHTML = text;
+  dyn1('.grid');
+  document.documentElement.removeAttribute("class");
+}
+</script>
+
+</head>
+<body onload='dynamicTest("grid-fragmentation-002.html", runTest)'></body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-dyn1-006.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html class="reftest-wait"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: test 006 dynamic remove/insert first item</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-006-ref.html">
+
+<script src="support/dyn.js"></script>
+<script>
+function runTest(text) {
+  document.body.innerHTML = text;
+  dyn1('.grid');
+  document.documentElement.removeAttribute("class");
+}
+</script>
+
+</head>
+<body onload='dynamicTest("grid-fragmentation-006.html", runTest)'></body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-dyn1-015.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html class="reftest-wait"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: test 015 dynamic remove/insert first item</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-015-ref.html">
+
+<script src="support/dyn.js"></script>
+<script>
+function runTest(text) {
+  document.body.innerHTML = text;
+  dyn1('.grid');
+  document.documentElement.removeAttribute("class");
+}
+</script>
+
+</head>
+<body onload='dynamicTest("grid-fragmentation-015.html", runTest)'></body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-dyn1-016.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html class="reftest-wait"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: test 016 dynamic remove/insert first item</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-016-ref.html">
+
+<script src="support/dyn.js"></script>
+<script>
+function runTest(text) {
+  document.body.innerHTML = text;
+  dyn1('.grid');
+  document.documentElement.removeAttribute("class");
+}
+</script>
+
+</head>
+<body onload='dynamicTest("grid-fragmentation-016.html", runTest)'></body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-dyn1-019.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html class="reftest-wait"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: test 019 dynamic remove/insert first item</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-019-ref.html">
+
+<script src="support/dyn.js"></script>
+<script>
+function runTest(text) {
+  document.body.innerHTML = text;
+  dyn1('.grid');
+  document.documentElement.removeAttribute("class");
+}
+</script>
+
+</head>
+<body onload='dynamicTest("grid-fragmentation-019.html", runTest)'></body>
+</html>

new file mode 100644
--- /dev/null
+++ b/layout/reftests/css-grid/grid-fragmentation-dyn1-020.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html class="reftest-wait"><head>
+  <meta charset="utf-8">
+  <title>CSS Grid Test: test 020 dynamic remove/insert first item</title>
+  <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1144096">
+  <link rel="help" href="https://drafts.csswg.org/css-grid/#pagination">
+  <link rel="match" href="grid-fragmentation-020-ref.html">
+
+<script src="support/dyn.js"></script>
+<script>

author	Mats Palmgren <mats@mozilla.com>
	Fri, 11 Mar 2016 17:39:28 +0100
changeset 288318	552aabbcd11631edd38087a55e8730db1384bdfc
parent 288317	5e3e2675488c1b089e82a442dfeee46da1152cf1
child 288319	50c03319c341910196103c4451f17299eb144313
push id	30079
push user	ryanvm@gmail.com
push date	Sat, 12 Mar 2016 20:24:19 +0000
treeherder	mozilla-central@d1d47ba19ce9 [default view] [failures only]
perfherder	[talos] [build metrics] [platform microbench] (compared to previous push)
bugs	1144096
milestone	48.0a1
first release with	nightly linux32 f0c0480732d3 / 48.0a1 / 20160314030215 / files nightly linux64 f0c0480732d3 / 48.0a1 / 20160314030215 / files nightly mac d1d47ba19ce9 / 48.0a1 / 20160313030418 / files nightly win32 d1d47ba19ce9 / 48.0a1 / 20160313030418 / files nightly win64 d1d47ba19ce9 / 48.0a1 / 20160313030418 / files
last release without	nightly linux32 946ed22cad04 / 48.0a1 / 20160312030405 / files nightly linux64 946ed22cad04 / 48.0a1 / 20160312030405 / files nightly mac 946ed22cad04 / 48.0a1 / 20160312030405 / files nightly win32 946ed22cad04 / 48.0a1 / 20160312030405 / files nightly win64 946ed22cad04 / 48.0a1 / 20160312030405 / files

layout/reftests/css-grid/grid-fragmentation-001-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-001.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-002-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-002.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-003-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-003.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-004-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-004.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-005-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-005.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-006-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-006.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-007-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-007.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-008-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-008.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-009-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-009.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-010-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-010.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-011-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-011.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-012-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-012.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-013-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-013.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-014-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-014.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-015-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-015.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-016-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-016.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-017-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-017.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-018-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-018.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-019-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-019.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-020-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-020.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-021-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-021.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-022.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-023-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-023.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-024-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-024.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-025-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-025.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-026-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-026.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-027.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-028-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-028.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-029-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-029.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-030-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-030.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-031-ref.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-031.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-002.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-006.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-015.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-016.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-019.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-020.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-021.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-023.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-024.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-026.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-027.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-028.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn1-029.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-018.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-019.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-020.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-021.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-022.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-023.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-025.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-026.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-027.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-028.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-029.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-030.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn2-031.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-001.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-002.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-003.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-007.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-009.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-017.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-019.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-021.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-023.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-026.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-027.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn3-028.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-001.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-004.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-005.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-015.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-019.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-021.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-023.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-026.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-027.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn4-028.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-005.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-007.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-008.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-016.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-019.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-021.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-023.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-026.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-027.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/grid-fragmentation-dyn5-028.html		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/reftest.list		file \| annotate \| diff \| comparison \| revisions
layout/reftests/css-grid/support/dyn.js		file \| annotate \| diff \| comparison \| revisions